St Marks and Doge’s palace Venice

I think there is plenty of info for both places in the RS books unless you are a stickler for details. That said, here's a hint about St. Mark's: take a backpack or some 'larger' bag that the guards won't let you take inside. There is a storage room that will keep your stuff (they say 1 hour but they have no way of knowing if you stay longer!). They'll give you a claim check - take it to the EXIT of St. Mark's and walk right in. Now, where is it: as you face the basilica there is a small courtyard to the left. The space that looks designated for concerts is where you'll find the storage room. It's free, by the way.

We found the info in RS guide book to be sufficient.
We've done paid tours for lots of things and never found any of them to be a waste of money. YMMV

You might consider the Secret Itinerary tour- we really enjoyed it. After the tour you are free to tour Doges Palace on your own-you are already in- no waiting in line there.
https://palazzoducale.visitmuve.it/en/pianifica-la-tua-visita/special-itineraries/secret-itineraries-tour/

For the Basilica you can book a timed entry for 3€- we did that with a time just after it opened- there was already a huge line- then did the Secret Itinerary tour at 11 I think? Worked well, we didn't wait anywhere.
https://basilicasanmarco.insidecom.it/en/attractions-in-veneto/tickets/skip-the-line-saint-marks-basilica/#choose

So for a total of 23€ per person we had a really interesting tour and no waiting in line- not a waste of money in my opinion

Thank you. Great suggestions.